I think most people think that the players set up in a particular defense be it 3/4 or 4/3 or 5/2 and have freedom to decide how they cover their guy.

This isn't so.
Of course their is the man or zone assignment with the option to design for particular cover guys to spy or a safety to determine which side of the field to cover, but each set has a soft or hard or jam option that is predetermined.

When those guys play off in a soft coverage it isn't their decision. It is predetermined and called by the D coordinators.

After the play is snapped and the ball is released then yes they will adjust but if you are already playing your soft coverage assignment, you are already at a major disadvantage with your angle off attack and closing time.

We need to be on our coaches for this poor play calling. It was PAINFULLY obvious that we needed to jamb the receivers and force that qb to make a much more difficult throw down field if anyone broke free.
This can open you up to being blocked on a toss sweep play but it beats just letting them soft toss 10 yarders down the field on you.
You DO have the option to mix it up once they stop the short crap.

I saw one play where Al Harris Jr. was deployed to jam the A&M receiver (11?). 11 beat the press man coverage and scored an easy TD. So maybe your just wrong about your coaching staff critique.